Alex Parvulescu created OAK-3904:
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Summary: Compaction Map predicate should use cached state for
evaluation
Key: OAK-3904
URL: https://issues.apache.org/jira/browse/OAK-3904
Project: Jackrabbit Oak
Issue Type: Bug
Components: segmentmk
Reporter: Alex Parvulescu
Attachments: tar-writer-trace.png
In the case of offline compaction, the Compactor predicate would try to
evaluate if a specific node is candidate for the map of not based on a set of
conditions.
To evaluate said conditions, the predicate currently uses the compacted state,
the one that was just written by the SegmentWriter [0], but this offers very
poor performance as this NodeState will be accessed from the TarWriter
directly, a very IO intensive call (no memory mapping, no caching of the
segment) [1].
A much better thing is to use the cached nodestate, in my local test (on a SSD)
this accounts for 15% of perf loss, I would imagine the gains are more
significant on a non-SSD disk.
[0]
https://github.com/apache/jackrabbit-oak/blob/trunk/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/segment/Compactor.java#L252
[1]
https://github.com/apache/jackrabbit-oak/blob/trunk/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/segment/file/TarWriter.java#L190
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